The present invention relates to processes for the continuous manufacture of fiber-reinforced tubing based on cellulose hydrate, in which fibrous tubing impregnated and coated with aqueous alkaline viscose solution is continuously coated on the surface thereof with a film of regenerating fluid, and the regenerating fluid forming the film causes a coagulation of the viscose and its chemical conversion into cellulose hydrate.
The invention also relates to equipment for carrying out the processes.
The use of the products, which can be manufactured by the processes according to the invention, as packaging material, in particular as artificial sausage casings, is a further subject of the invention.
In the known processes for the manufacture of fiber-reinforced cellulose hydrate tubing, the fibrous tubing, to the outside of which viscose solution has been applied by means of an annular die and which has thus been impregnated and coated with viscose solution, is passed through a trough of sufficiently long dimensions, which is filled with regenerating fluid. In the bottom of the trough, rotatably mounted guide rolls are provided. The tubing on immersion into the trough filled with regenerating fluid is first deflected into a horizontal orientation with the aid of the first guide roll and then is deflected into a vertical orientation by the second guide roll, after which it is passed out of the trough again. The application is here carried out in such a way that initially a certain quantity of regenerating fluid is enclosed within the cavity of the tubing to which it is to be applied.
During the period in which the tubing runs through the regenerating fluid present in the trough, the surface of the tubing is in direct contact with a large quantity of regenerating fluid, and there is no substantial relative movement between this fluid and the wall of the viscose-treated fibrous tubing which is moved along the longitudinal axis.
In the known processes, the regenerating fluid is continuously fed into the cavity of the tubing on the underside of the take-off roll and is extracted on the side of the spinning die below the spinning die, so that there is always largely spent stagnant regenerating agent in the ascending part of the tubing. The regenerating agent acting on the outside of the tubing has a substantially uniform concentration. The concentration of the regenerating fluid acting on the outside of the tubing is, however, lower than that in the cavity of the tubing in order to ensure a circular cross-section of the tubing.
Gases formed during the process of coagulating and regenerating the viscose by the action of the regenerating fluid rise as gas bubbles both in the regenerating fluid in the cavity of the tubing and in the regenerating fluid present in the trough. These gas bubbles are extracted and diluted with air above the surface of the regenerating fluid.
The disadvantages of the known processes are thus the following:
1. The concentration of solute in the regenerating fluid acting on the inside of the tubing must be greater than that on the outside of the tubing.
2. To ensure an optimum course of coagulation during the action of the regenerating fluid on the viscose solution, the regenerating fluid must contain the solute in relatively small quantities in order to avoid undesired secondary phenomena which readily occur if the coagulation is excessively fast--for example vigorous gas evolution.
3. To remove the gases formed during the coagulation process in the deswelling water, the cavity of the tubing must be slit open at an undesired frequency in order to be able to discharge the said media therefrom; such slitting of the tubing is undesirable because it leads to an interruption in the course of the process and to undesired slits in the tubing which must be secured together again.
4. There is virtually no relative movement between the surface of the tubing and the quantity of regenerating fluid adjacent thereto at a particular time.
5. Because of the relatively large volume of regenerating fluid in the trough, a change in the sulfuric acid concentration of the regenerating fluid can be attained only after a relatively long time.
6. Due to unavoidable fluctuations in production, such as the tubing tearing off and the like, the concentration of the regenerating fluid in the trough must be readjusted relatively frequently since the more highly concentrated regenerating fluid present in the cavity of the tubing passes into that present in the bath and leads in the latter to a higher concentration of solute in the fluid.